Kinematic markers III: Extension Nodes

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Columnar basalts at Racoșul de Jos/ Alsórákos are yielding a 1200 ka to 600 ks old (Harangi et al., 2013)  effusive product in one of the  Perșani Mountain tension nodes, tracing the location of cross-cutting strike-slip  faults

Columnar basalts at Racoșul de Jos/ Alsórákos are yielding a 1200 ka to 600 ka old (Harangi et al., 2013) effusive product in one of the Perșani Mountain tension nodes, tracing the location of cross-cutting strike-slip faults

In the GSST approach, rising of magmas is related to the opening of crustal scale tension fractures. Because pure shear related stress field and deformation is unlikely to exist in nature, even within compressional belts there will exist some transtensional fracture components, which are characterized by significantly lower stress values. These tension fractures always form perpendicularly to the σ3 direction, and will serve as pathways for rising of magmas.

Cross-cutting fault systems are quite common in nature. While in regional compressional fault intersections stress nodes may form, in tensional fault intersections, extension nodes may appear. Here, in these extension nodes magmas have the highest chance to rich to the surface. As a consequence, volcanic craters are the best markers of regional extension nodes. In addition to volcanic craters, other parts of the volcanic build-ups may also serve as passive kinematic indicators, because of the pronounced hardness and brittleness of lavas and volcano sedimentary successions, in comparison to the surrounding environment.

Example: Columnar basalts at Racoșul de Jos/ Alsórákos are yielding a Pleistocene, 1200 ka to 600 ks old (Harangi et al., 2013) effusive product in one of the Perșani Mountain tension nodes, tracing the location of cross-cutting strike-slip faults.

Published in: Kovács, J.Sz., 2015 (in press), Elements of Global Strike-Slip Tectonics: a Quasi-Neotectonic Analysis, Journal of Global Strike-Slip Tectonics, v1., Szekler Academic Press, Sfintu Gheorghe.

Kinematic markers II: Stress Nodes

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Fig2Stress Node Map

There are at least 20 locations in Europe where the EMSC earthquake database is recording a spatial concentration of earthquake epicenters, like in the Vrancea Stress Node in Romania. We term these high activity seismogenic locations as ‘stress nodes’, because earthquake epicenters are sites of stress accumulation and release. High velocity bodies below a strike-slip zone are not uncommon (Hadley and Kanamori, 1977, in Kearey and Vine, 1996). Hadley has documented a high velocity body below the Transverse Ranges which was seismically active even at 100km.

A similar phenomenon happens in the Vrancea area, which serves as a meeting point for three different nanoplates, hence cross-cutting strike-slip faults. In this area, seismic gaps should be interpreted as oversteps of faults, as suggested in the case of the Calaveras fault (Reasenberg and Ellsworth, 1982). The occurrence of stress nodes in corner positions of microplates and nanoplates could be already predicted by GSST logics as well, without consulting the earthquake database, because significant structural deformation is also more likely to be present in corner locations.

Just nearby the Haute Provence Stress Node, in Southeastern France, 6 distinct deformation domains were isolated from the inversion of 89 focal mechanism (Baroux et al., 2001), which fits completely into the expected structural configuration, outlined by GSST techniques. This great variety of the recorded deformation domains is depicting the whole strike-slip stress field, including conjugate fault activity.

In the current study we have isolated the following Stress Nodes: 1) Vrancea Stress Node, Eastern Carpathians, Romania, 2) South Silesian Stress Node, Poland, 3) Lower Silesian Stress Node, Poland, 4) Po Valley Stress Node, Italy, 5) Cuneo Stress Node, Alpi-Marittime, Italy, 6) Haute Provence Stress Node, Alpes-de-Haute-Provence, France, 7) Pyrenees Stress Node, Spain, 8) Umbria Stress Node, Apennines, Italy, 9) Lipari Stress Node, Tyrrhenian Sea, Italy, 10) Monte Negro Stress Node, 11) Albanian Stress Node, 12) Gulf of Corinth Stress Node, Greece, 13) Keffalonia Stress Node, Greece, 14) Zakinthos Stress Node, Greece, 15) Crete Cluster of Stress Nodes, Greece, 16) Soma Stress Node, Turkey, 17) Şenköy Stress Node, Turkey, 18) Çameli Stress Node, Turkey, 19) Sapientza Stress Node, Greece, 20) Pamukkale Stress Node, Turkey, 21) Elazig Stress Node, Turkey, 22) Tabriz Stress Node, 23) Van Lake Stress Node, Turkey, 24) Qushm Stress Node, Iran, 25) Karakul Stress Node, Pamir Mts. China-Tajikistan, 26) Badakhshan Stress Node, Pamir Mts., Tajikistan, 27) Islamabad Stress Node, Himalaya Mts., Pakistan.

A systematic description of stress nodes listed above does not represent the objective of the present study.

Published in: Kovács, J.Sz., 2015 (in press), Elements of Global Strike-Slip Tectonics: a Quasi-Neotectonic Analysis, Journal of Global Strike-Slip Tectonics, v1., Szekler Academic Press, Sfintu Gheorghe.

Kinematic Markers I: Geomorphology

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Fig6 Torocko faultWorld topography is shaped by a complex interaction of various physical and chemical processes, where climate plays an important role. Different rocks may deform in very different way under same conditions. Structural stress has its important role in preconditioning the ultimate style of deformation in rocks, because fracture systems not only enhance, but may also drive erosional processes, especially in hard rocks, like limestones.

Fracture systems in lowlands may be hidden by young sediments; fault scarps in deserts are rapidly covered by mobile sand, while on oceanic passive margins delta systems may shed sediment over them. Fluvial channels also migrate autocyclically in the alluvial plain, hence cannot be used with automatism in geomorphological studies, however automatic techniques might be useful in delimiting recently uplifted areas. The higher the sediment input, the less chance we have to capture neotectonic events. Because on the central part of oceanic basins sediment input is extremely low, fault scars can be traced most easily on oceanic floors.

Despite the presence of inconvenient obstacles, there still remain several principles according to which geomorphological elements can be used in tracing worldwide quasi-neotectonic lineaments: 1) sharpness of geomorphological lineaments, 2) regional continuity, 3) linkage of linear geomorphological lineaments to other point-type markers, 4) inter-regional altitude contrast, 5) abrupt changes in watercourse of larger rivers, 6) abrupt changes in shorelines, 7) abrupt changes in mountain ridges, 8) presence of extensional or contractional duplexes.

In order to map strike-slip lineaments of the world we constructed digital elevation models from SRTM data for Eurasia and Northern Africa; oceanic domains and the other parts of the world were approximated using Google Earth data.

Example:

Trascăului Mountains, which delimit the Transylvanian basin from west, belong to the Western Transylvanides and form an obducted tectonic unit (Săndulescu, 1984) of the Apuseni Mts. range, exhibiting an oceanic (ophiolitic) basement. The study area around the Piatra Secuiului Peak is made up from slope and shelf-margin deposits of an Upper Jurassic-Lower Cretaceous carbonate platform (Săsăran, 2006). Given the well-cemented and compacted nature of the sedimentary succession, weathering plays only a secondary role in shaping the landscape of the Trascăului Mountains, thus regional neotectonic lineaments can be recognized at the local scale as well (Fig. 11, 12). Local fault lineaments delineated in plain view by geomorphological techniques on the Google Earth topography can be identified on field as well.

Published in: Kovács, J.Sz., 2015 (in press), Elements of Global Strike-Slip Tectonics: a Quasi-Neotectonic Analysis, Journal of Global Strike-Slip Tectonics, v1., Szekler Academic Press, Sfintu Gheorghe.

 

Mantle Origin of CO2 and Carbonate Budget of Oceans and Travertine Deposits – Examples from Turkey and Szeklerland

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The Pamukkale Travertine was deposited along the Burdur-Fethye fault zone. The main source of the significant amount of CO2 converted into bicarbonate should be of mantle origin, as proven by the nearby presence of borate deposits in the Bigadiç borate Basin.

Carbonate budget in the oceans of the Earth and in continental domains, as well, basically depends on the availability of CO2 in aqueous solutions, which might be a function of the mantle CO2 release by oceanic floor volcanic activity, in a given geological period. Wilson includes the enrichment in volatiles, halogens and CO2, among the general characteristics of continental rift zone magmatism (Wilson, 1989). Solubility of CO2 in magmas increases with pressure and magma alkalinity (Lowenstern, 2001).

Mantle origin CO2 is commonly present in active strike-slip zones, either as bicarbonate ion in aqueous solutions, or as dry CO2, and may give birth to significant continental carbonate deposits in the form of travertines, like in Pamukkale, Turkey, or the Yellowstone carbonate travertines in the USA. For example, the Ol Doinyo Lengai volcano of the East African Rift, Tanzania, is producing natrocarbonatite lava, accompanied by a flux of 6000–7200 tonnes CO2 d−1 (Koepenick et al., 1996). It is very difficult to disproof the mantle origin of these enormous CO2 fluxes.

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Small size Holocene carbonate tufa dome at Tălișoara/ Olasztelek, Szeklerland, Romania

Distribution of massive CO2 occurrences and that of larger carbonate tufa domes is related to deep crustal faults, and thus surface carbonate tufa deposits can be used to trace deep seated crustal faults, hence we consider them as integral parts of the GSST mapping techniques. A minor carbonate tufa dome is above from Tălișoara/ Olasztelek, which together with the Bálványos carbonate tufa domes delineate a major W to E trending deeper crustal fault system in Szeklerland/ Romania. Another synthetic fault to the master is coming from the Racoș/ Alsórákos neovolcanic area via the Ozunca Băi/ Uzonkafürdő carbonate tufa dome.

Published in: Kovács, J.Sz., 2015 (in press), Elements of Global Strike-Slip Tectonics: a Quasi-Neotectonic Analysis, Journal of Global Strike-Slip Tectonics, v1., Szekler Academic Press, Sfintu Gheorghe.